Caracas Gringo warned in October 2009 that the Guri Dam was at growing risk of suffering a catastrophic failure that could destroy most of its hydro-power generation infrastructure. The risk that Guri could suffer a catastrophic failure is substantially greater now than it was almost seven months ago.

The catastrophic failure of a single turbine could trigger a collapse, shutting down Guri completely and possibly forcing Edelca to shut down the Caruachi and Macagua hydropower complexes downriver from Guri. This would deprive Venezuela of almost 70% of its power supply.

Officials at Guri report that Turbine No. 8, a 400 MW-capacity Francis turbine, came very close to suffering a catastrophic failure on 2 May.

The turbine, which has a history of “cavitation” (i.e. vibration), started to vibrate “very violently,” an Edelca source says. Fortunately for Venezuela, quick-thinking Edelca operators shut down the turbine immediately. But the vibrations were so strong that the turbine and surrounding concrete infrastructure appear to have suffered substantial damage, according to the Edelca source.

Corpoelec says that the incident remains under investigation by the national intelligence service (Sebin), and declines to say when Turbine No. 8 might be restarted. But our Edelca sources report that the turbine could be out of service for months while the damages are assessed and repairs are completed. Meanwhile, No. 8’s shutdown means that nine of Guri’s 20 hydropower generation turbines currently are out of service.

Our Edelca sources also say that No. 8 isn’t the only turbine with vibration problems.

Corpoelec also declines to say when Planta Centro’s thermal power generation unit No. 4 will be restarted. No. 4 was shut down on 5 May due to a transformer explosion and fire at the 400 kV/230 kV sub-station near Moron. At the time, No. 4 was generating 320 MW, according to plant operator Cadafe.

Half of Puerto Cabello was left in the dark, and power still has not been restored completely as we write this post. It was the fourth major accident at Planta Centro since 1 January 2010. Planta Centro’s rated generation capacity is 2,000 MW spread among five 400 MW thermal power generation units, but it usually generates between 150 MW and 300 MW from Units 3 and 4.

These two incidents have taken 720 MW of power offline, perhaps for months.

Edelca sources say that Corpoelec has given orders to increase the volume of water flowing through Guri’s 11 operational hydropower turbines to offset the loss of No. 8’s 400 MW and the loss of the 320 MW that Planta Centro’s No. 4 was generating.

But raising the volume of water flowing through Guri’s turbines implies greater risks of more equipment breakdowns. Necessary maintenance work must be suspended, and old turbines strained from over-use come closer to the point of unexpected failures.